Conventionally, electronic equipment such as a mobile phone, a smartphone, and a tablet PC have used an RFID (Radio Frequency Identification) antenna module to provide a near field contactless communication function. An antenna module for providing a contactless charging function is also being used more and more popularly.
Such an antenna module communicates with an antenna coil embedded in a transmitter of a power-transmitting device (hereinafter, simply called a reader/writer or the like) of a reader/writer and a contactless charging system, by utilizing inductive coupling. That is to say, the antenna module is capable of receiving a magnetic field from the reader/writer or the like by an antenna coil, converting energy of the received magnetic field to power to drive an IC serving as a communication processing unit, and charging a battery of a power-receiving device included in the contactless charging system.
For reliable communication, the antenna module needs to receive, from the reader/writer or the like, at least a certain level of magnetic flux by the antenna coil. Accordingly, the antenna module according to the conventional technique includes a loop coil that is located in a housing of the mobile phone to receive magnetic flux from the reader/writer or the like.
For example, Patent Literature 1 proposes a method for improving characteristics of a loop antenna embedded in a portable terminal apparatus, the method including arranging a flexible cable or a flat cable to surround the built in battery.